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  • 1
    Publication Date: 2024-01-29
    Type: Book chapter , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2024-02-07
    Description: In 2016, the research ice-breaker Polarstern surveyed the submerged peaks of the permanently ice-covered Langseth Ridge, a tectonic feature comprising the Karasik seamount and two deeper seamount peaks, abutting the Gakkel ultra-slow spreading ridge (87°N 62°E to 85.5°N 57.4°E)1. A towed marine camera sled and a hybrid remotely operated vehicle revealed these peaks to be covered by a dense demosponge community, at first glance reminiscent of North Atlantic Geodia grounds (sensu2). Sponges were observed on top of a thick layer of spicule mat (Figure 1 and Video S1), intermixed with underlying layers of empty siboglinid tubes and bivalve shells, a substrate covering almost the entire seafloor. We observed trails of densely interwoven spicules connected directly to the underside or lower flanks of sponge individuals (Figure 1), suggesting these trails are traces of motile sponges. This is the first time abundant sponge trails have been observed in situ and attributed to sponge mobility. Given the low primary production in this permanently ice-covered region, these trails may relate to feeding behavior and/or a strategy for dispersal of juveniles. Such trails may remain visible for long periods given the regionally low sedimentation rates.
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2024-02-07
    Description: Sponges produce distinct fatty acids (FAs) that (potentially) can be used as chemotaxonomic and ecological biomarkers to study endosymbiont-host interactions and the functional ecology of sponges. Here, we present FA profiles of five common habitat-building deep-sea sponges (class Demospongiae, order Tetractinellida), which are classified as high microbial abundance (HMA) species. Geodia hentscheli, G. parva, G. atlantica, G. barretti, and Stelletta rhaphidiophora were collected from boreal and Arctic sponge grounds in the North-Atlantic Ocean. Bacterial FAs dominated in all five species and particularly isomeric mixtures of mid-chain branched FAs (MBFAs, 8- and 9-Me-C16:0 and 10- and 11-Me-C18:0) were found in high abundance (together ≥ 20% of total FAs) aside more common bacterial markers. In addition, the sponges produced long-chain linear, mid- and a(i)-branched unsaturated FAs (LCFAs) with a chain length of 24‒28 C atoms and had predominantly the typical Δ5,9 unsaturation, although the Δ9,19 and (yet undescribed) Δ11,21 unsaturations were also identified. G. parva and S. rhaphidiophora each produced distinct LCFAs, while G. atlantica, G. barretti, and G. hentscheli produced similar LCFAs, but in different ratios. The different bacterial precursors varied in carbon isotopic composition (δ13C), with MBFAs being more enriched compared to other bacterial (linear and a(i)-branched) FAs. We propose biosynthetic pathways for different LCFAs from their bacterial precursors, that are consistent with small isotopic differences found in LCFAs. Indeed, FA profiles of deep-sea sponges can serve as chemotaxonomic markers and support the concept that sponges acquire building blocks from their endosymbiotic bacteria.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 4
    Publication Date: 2021-10-03
    Description: Sponges produce distinct fatty acids (FAs) that (potentially) can be used as chemotaxonomic and ecological biomarkers to study endosymbiont-host interactions and the functional ecology of sponges. Here, we present FA profiles of five common habitat-building deep-sea sponges (class Demospongiae, order Tetractinellida), which are classified as high microbial abundance (HMA) species. Geodia hentscheli, G. parva, G. atlantica, G. barretti, and Stelletta rhaphidiophora were collected from boreal and Arctic sponge grounds in the North-Atlantic Ocean. Bacterial FAs dominated in all five species and particularly isomeric mixtures of mid-chain branched FAs (MBFAs, 8- and 9-Me-C16:0 and 10- and 11-Me-C18:0) were found in high abundance (together ≥ 20% of total FAs) aside more common bacterial markers. In addition, the sponges produced long-chain linear, mid- and a(i)-branched unsaturated FAs (LCFAs) with a chain length of 24‒28 C atoms and had predominantly the typical Δ5,9 unsaturation, although the Δ9,19 and (yet undescribed) Δ11,21 unsaturations were also identified. G. parva and S. rhaphidiophora each produced distinct LCFAs, while G. atlantica, G. barretti, and G. hentscheli produced similar LCFAs, but in different ratios. The different bacterial precursors varied in carbon isotopic composition (δ13C), with MBFAs being more enriched compared to other bacterial (linear and a(i)-branched) FAs. We propose biosynthetic pathways for different LCFAs from their bacterial precursors, that are consistent with small isotopic differences found in LCFAs. Indeed, FA profiles of deep-sea sponges can serve as chemotaxonomic markers and support the concept that sponges acquire building blocks from their endosymbiotic bacteria.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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  • 5
    Publication Date: 2023-03-13
    Description: Located 10° further north than any sponge ground yet reported, the population, primarily comprising Geodia parva, G. hentscheli and Stelletta rhaphidiophora individuals, covers the great majority of the Langseth Ridge from ∼1,000 m upward, to a shallowest peak of 580 m depth, at very high abundance1. Sizes of individual sponges varied, with a median diameter of 17 cm (± 0.10 cm SE, n = 10,839, and IQR 11–25 cm); the maximum diameter observed was 110 cm and the smallest were just over 1 cm. This size range equates to a median wet weight of 1.4 kg (± 0.12 kg SE, n = 10,839; IQR 0.4–5 kg; Figure S1). Sponges are opportunistic feeders; although they efficiently retain particulates by filter feeding, dissolved organic matter in seawater often represents the main food source2. The low productivity and nutrient fluxes that characterize this region — due to high latitude, permanent sea ice cover, and distance from land — raise the question of how this abundant biomass is maintained. We analyzed the many trails of interwoven spicules across the seamount peaks. Trails were observed to be several centimeters in height and up to meters in length, often connected directly to living sponges. These trails were particularly visible in areas of low sponge density, that is, where trails crossed bedrock in areas sparsely covered by sediments or organic debris (Figure 1A–E and Video S1). Spicule trails in areas of denser sponge aggregation exhibited a higher vertical thickness than observed elsewhere (Figures 1F and S1A, and Video S1). Our observations also suggest that the spicule trails correlated with the distribution of smaller juvenile sponges (Figure S1A).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev , info:eu-repo/semantics/article
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  • 6
    Publication Date: 2023-06-21
    Description: The Central Arctic Ocean is one of the most oligotrophic oceans on Earth because of its sea- ice cover and short productive season. Nonetheless, across the peaks of extinct volcanic seamounts of the Langseth Ridge (87°N, 61°E), we observe a surprisingly dense benthic biomass. Bacteriosponges are the most abundant fauna within this community, with a mass of 460 g C m−2 and an estimated carbon demand of around 110 g C m−2 yr−1, despite export fluxes from regional primary productivity only sufficient to provide 〈1% of this required carbon. Observed sponge distribution, bulk and compound-specific isotope data of fatty acids suggest that the sponge microbiome taps into refractory dissolved and particulate organic matter, including remnants of an extinct seep community. The metabolic profile of bacter- iosponge fatty acids and expressed genes indicate that autotrophic symbionts contribute significantly to carbon assimilation. We suggest that this hotspot ecosystem is unique to the Central Arctic and associated with extinct seep biota, once fueled by degassing of the volcanic mounts.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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